# Assessing diagnostic accuracy for asthma with home spirometry in primary care

## TL;DR

This study tested how well home spirometry can diagnose asthma in primary care, finding that diurnal variability testing offered the best balance of accuracy.

## Contribution

The study introduces a novel evaluation of home spirometry's diagnostic accuracy for asthma in primary care settings.

## Key findings

- Home spirometry with diurnal variability testing showed the strongest balance of sensitivity and specificity for asthma diagnosis.
- Only 9% sensitivity was observed for bronchodilator responsiveness (BDR), while peak expiratory flow (PEF) showed 76% sensitivity.
- Overall, 58% of participants were diagnosed with asthma after assessments and trial treatment.

## Abstract

The aim was to evaluate the diagnostic accuracy of lung function measurements for asthma in primary care, including trial treatment. Undiagnosed patients seeking care for asthma-like symptoms were assessed at primary healthcare centers in Sweden. Participants underwent remote or in-clinic spirometry with bronchodilator responsiveness testing (BDR), remote diurnal variability testing of forced expiratory volume in 1 s (FEV1) and peak expiratory flow (PEF) over 2–4 weeks using a home spirometry system; and if necessary, three-months trial treatment with inhaled corticosteroids. Overall, 71/123 (58%) were diagnosed with asthma. When comparing patients by asthma diagnosis, sensitivity and specificity for documented diagnosis were 9% (95% CI 3–17) and 100% (93–100) for BDR; 61% (48–72) and 58% (43–71) for FEV₁; and 76% (64–85) and 69% (55–81) for PEF. Diurnal variability testing via home spirometry showed the strongest balance among sensitivity and specificity for asthma.